This invention relates to a process for converting fine particulates comprising hydrolyzable metal halides (including oxyhalides, if present) into readily-handled granules in economical manner.
Typically such particulates today are waste products, eg. chlorinator byproducts (often collected from a cyclone separator, thus "cyclone solids") from the chlorination of titaniferous materials such as a chlorination of rutile or ilmenite ore with coke to make pigmentary TiO.sub.2 or the beneficiation of ilmenite ore with chlorine and coke. It is elementary chemistry to expect many metal chlorides to hydrolyze with water. Titanium tetrachloride itself has been hydrolyzed deliberately, for example, to generate TiO.sub.2 and HCl.
The term "cyclone solids" is derived from the collection of these fines by cyclone separator from a vapor stream, often out of a fluidized bed reactor, although other conventional reactor and collector types are useful also, so the term need not be construed narrowly. They usually are about 120 mesh (U.S. Standard Sieve) or finer. They dust, often tend to be hygroscopic, and usually fume obnoxiously in humid air to give off some deleterious and corrosive hydrogen chloride. Representative titaniferous ore chlorinator byproducts will contain unreacted (and/or partially reacted) ore, coke, ferrous chloride, ferric chloride, and minor amounts of the chlorides and oxychlorides of vanadium, chromium, niobium, titanium, magnesium, aluminum, silicon, and zirconium (the vanadium usually thought of as being in the vanadyl (VO) form). If sufficient of these wastes can be supplied to a central location, the recovery of at least minor components such as vanadium and/or niobium therefrom can be attractive.
Chlorination of various alumina- and zirconia-bearing material with carbon can give rise to related wastes which can be processed in accordance with the instant invention.
Mechanical agglomeration or granulation assisted by a liquid binding agent such as a very small proportion of water is a well-known practice for use with nonhydrolyzable solids such as carbon black, glass batch components (oxides, carbonates, silicates, and the like), foods, and many other substances. In some instances the water appears to assist in forming nuclei upon which spheres or agglomerates build.
A variety of things must occur to make the instant process practical. Thus, there must be substantial hydrolysis of the metal halides. Concommitant with this is the evolution of heat and corrosive byproduct vapors, the heat evolution being of assistance for removal of a modest excess of water (which is desirable to drive the hydrolysis reaction); and, in addition to the foregoing, agglomeration must occur to make comparatively rugged granules that can be handled readily with safety in covered, preferably steel, equipment with little or no dusting or fuming. The instant process accomplishes these things efficiently and economically. Ambient transit conditions are ambient air temperature and humidity in conventional transporting and storage equipment.